Cooling plates of the above type (see Andonyev S. M. et al., Okhlazhdenie domennykh pechei, Moscow, "Metallurgia", 1972, s.216-220) are manufactured by pouring cast iron around steel cooling pipes so as to embed them in said cast iron, which forms a body of the plate. Such plates are cast either flat or provided with supporting projections. Said pipes are also used for cooling the projection, for which end these pipes are bent so as to enter the projection body. Cooling of said projections may also be effected through separate cooling pipes.
The cooling plates of the above type have portions which are located between the cooling pipes and at the elbows thereof, in which portions there exist a non-uniform thermal field and a low rate of heat removal. The non-uniform thermal field produces thermal stresses within the plate and pipes. The thermal stresses are also caused by the fact that cast iron and steel have different coefficients of thermal expansion. Furthermore, in the zone of outlet portions of the pipes there exist residual stresses formed during the process of pouring cast iron around the steel pipes. In the process of manufacturing the cooling plates the steel pipes may be carburized and, consequently loose plasticity in spite of application of protective coatings, e.g. marshalite ones. The above disadvantages result in a shorter service life of the cooling plates.
In the operation of the prior art cooling plates, in the case of burning-through of the cooling pipes there arise problems of finding and disconnecting the burnt pipes, and in particular the pipes of the supporting projections, which pipes are damaged first of all.
The object of the invention is to provide a more stable cooling plate of the above type due to a more uniform and intensive cooling thereof.
The object set forth is attained in the provision of a cooling plate of the above type for metallurgical furnaces, wherein according to the invention a duct for a cooling medium is constructed as an upwardly extending channel closed with cover plates at the rear and end sides thereof, said channel being cast into the plate metal so that the rear cover plate is not embedded in metal, branch pipes for feeding a cooling medium into the duct and for discharging the same from said duct being provided on the rear cover plate.
The cooling plate of such a design ensures a more uniform and reliable cooling due to the elimination of non-cooled angular portions. Since the duct for the cooling medium, constructed in the form of a channel, can cover a large area of the plate, so that the problem of interpipe distances is completely solved. The provision of the branch pipes for feeding and discharging the cooling medium on the rear side of the cover plate which is not embedded in metal, eliminates the problem of residual stresses in the plate and the pipes, said stresses being caused by jamming of the discharge portions of the pipes and by different coefficients of elongation of cast iron and steel, if these materials are utilized. Besides, a large mass of the channels as compared with that of the cooling pipes in the prior art cooling plates ensures a more intensive solidification of cast iron used for cooling plates, thereby resulting in the decrease in carburization of the ducts for the cooling medium.
It is preferred to introduce the cooling pipe of the projection, forming an enclosed loop of circulation of the cooling medium, into the duct for the cooling medium. Such an arrangement makes it possible to eliminate labour-consuming operations of finding and disconnecting the burnt pipes of the bearing projection, since the above pipes are not directly connected with an external system for feeding the cooling medium, water in particular. In this case, uncontrolled entrance of water into the furnace is eliminated.
To increase the reliability of cooling it is expedient that the duct for the cooling medium be extending over the whole height of the plate.